WO 2007/096295 A1 discloses a grinding wheel for grinding a required profile in the side of a channel that extends through a body, the wheel taking the form of a cup, the cup having a base and a wall that delimit the hollow of the cup, the wall being circular in form, the circular form of the wall being centered on the axis of rotation of the wheel, the exterior of the wall being abrasive and having a profile corresponding to the required profile in the side of the channel, in use of the grinding wheel a section of the wall being placed in the channel so that the abrasive exterior of the section bears against the side of the channel in which the profile is to be ground, grinding of the profile being achieved by rotation of the wheel.